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                                                                    Exhibit 10.5


                                  MITOKOR, INC.
                        2002 EMPLOYEE STOCK PURCHASE PLAN


         1.       ESTABLISHMENT, PURPOSE AND TERM OF PLAN.

                  1.1      ESTABLISHMENT. The MitoKor, Inc. 2002 Employee Stock
Purchase Plan (the "PLAN") is hereby established effective as of the effective
date of the initial registration by the Company of its Stock under Section 12 of
the Securities Exchange Act of 1934, as amended (the "EFFECTIVE DATE").

                  1.2      PURPOSE. The purpose of the Plan is to advance the
interests of the Company and its stockholders by providing an incentive to
attract, retain and reward Eligible Employees of the Participating Company Group
and by motivating such persons to contribute to the growth and profitability of
the Participating Company Group. The Plan provides such Eligible Employees with
an opportunity to acquire a proprietary interest in the Company through the
purchase of Stock. The Company intends that the Plan qualify as an "employee
stock purchase plan" under Section 423 of the Code (including any amendments or
replacements of such section), and the Plan shall be so construed.

                  1.3      TERM OF PLAN. The Plan shall continue in effect until
the earlier of its termination by the Board or the date on which all of the
shares of Stock available for issuance under the Plan have been issued.

         2.       DEFINITIONS AND CONSTRUCTION.

                  2.1      DEFINITIONS. Any term not expressly defined in the
Plan but defined for purposes of Section 423 of the Code shall have the same
definition herein. Whenever used herein, the following terms shall have their
respective meanings set forth below:

                           (a)      "BOARD" means the Board of Directors of the
Company. If one or more Committees have been appointed by the Board to
administer the Plan, "Board" also means such Committee(s).

                           (b)      "CODE" means the Internal Revenue Code of
1986, as amended, and any applicable regulations promulgated thereunder.

                           (c)      "COMMITTEE" means a committee of the Board
duly appointed to administer the Plan and having such powers as specified by the
Board. Unless the powers of the Committee have been specifically limited, the
Committee shall have all of the powers of the Board granted herein, including,
without limitation, the power to amend or terminate the Plan at any time,
subject to the terms of the Plan and any applicable limitations imposed by law.

                           (d)      "COMPANY" means MitoKor, Inc., a Delaware
corporation, or any successor corporation thereto.


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                           (e)      "COMPENSATION" means, with respect to any
Offering Period, base salary and commissions, including any base salary or
commissions deferred under any program or plan established by a Participating
Company, including, without limitation, any plan described in Section 401(k) or
Section 125 of the Code. Compensation shall be limited to amounts actually
payable in cash directly to the Participant or deferred by the Participant
during the Offering Period. Compensation shall not include overtime, bonuses,
annual awards, profit sharing, other incentive payments, shift premiums,
long-term disability, workers' compensation, moving allowances, payments
pursuant to a severance agreement, termination pay, relocation payments, sign-on
bonuses, expense reimbursements, the cost of employee benefits paid by a
Participating Company, tuition reimbursements, imputed income arising under any
benefit program, contributions made by a Participating Company under any
employee benefit plan, income directly or indirectly received pursuant to the
Plan or any other stock purchase or stock option plan, or any other compensation
not included in base salary and commissions.

                           (f)      "ELIGIBLE EMPLOYEE" means an Employee who
meets the requirements set forth in Section 5 for eligibility to participate in
the Plan.

                           (g)      "EMPLOYEE" means a person treated as an
employee of a Participating Company for purposes of Section 423 of the Code. A
Participant shall be deemed to have ceased to be an Employee either upon an
actual termination of employment or upon the corporation employing the
Participant ceasing to be a Participating Company. For purposes of the Plan, an
individual shall not be deemed to have ceased to be an Employee while on any
military leave, sick leave, or other bona fide leave of absence approved by the
Company of ninety (90) days or less. If an individual's leave of absence exceeds
ninety (90) days, the individual shall be deemed to have ceased to be an
Employee on the ninety-first (91st) day of such leave unless the individual's
right to reemployment with the Participating Company Group is guaranteed either
by statute or by contract.

                           (h)      "FAIR MARKET VALUE" means, as of any date:

                                    (i)      If the Stock is then listed on a
national or regional securities exchange or market system or is regularly quoted
by a recognized securities dealer, the closing sale price of a share of Stock
(or the mean of the closing bid and asked prices if the Stock is so quoted
instead) as quoted on the Nasdaq National Market, the Nasdaq SmallCap Market or
such other national or regional securities exchange or market system
constituting the primary market for the Stock, or by such recognized securities
dealer, as reported in THE WALL STREET JOURNAL or such other source as the
Company deems reliable. If the relevant date does not fall on a day on which the
Stock has traded on such securities exchange or market system or has been quoted
by such securities dealer, the date on which the Fair Market Value is
established shall be the last day on which the Stock was so traded or quoted
prior to the relevant date, or such other appropriate day as determined by the
Board, in its discretion.

                                    (ii)     If, on the relevant date, the Stock
is not then listed on a national or regional securities exchange or market
system or regularly quoted by a recognized securities dealer, the Fair Market
Value of a share of Stock shall be as determined in good faith by the Board.


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                                    (iii)    Notwithstanding the foregoing, the
Fair Market Value of a share of Stock on the Effective Date shall be deemed to
be the public offering price set forth in the final prospectus filed with the
Securities and Exchange Commission in connection with the Company's initial
public offering of the Stock.

                           (i)      "INITIAL OFFERING PERIOD CASH EXERCISE
NOTICE" means a written notice in such form as specified by the Company, which
states a Participant's election to exercise, as of the next Purchase Date, a
Purchase Right granted to such Participant with respect to the Initial Offering
Period.

                           (j)      "OFFERING" means an offering of Stock as
provided in Section 6.1.

                           (k)      "OFFERING DATE" means, for any Offering, the
first day of the Offering Period.

                           (l)      "OFFERING PERIOD" means a period established
in accordance with Section 6.

                           (m)      "PARENT CORPORATION" means any present or
future "parent corporation" of the Company, as defined in Section 424(e) of the
Code.

                           (n)      "PARTICIPANT" means an Eligible Employee who
has become a participant in an Offering Period in accordance with Section 7 and
remains a participant in accordance with the Plan.

                           (o)      "PARTICIPATING COMPANY" means the Company or
any Parent Corporation or Subsidiary Corporation designated by the Board as a
corporation the Employees of which may, if Eligible Employees, participate in
the Plan. The Board shall have the sole and absolute discretion to determine
from time to time which Parent Corporations or Subsidiary Corporations shall be
Participating Companies.

                           (p)      "PARTICIPATING COMPANY GROUP" means, at any
point in time, the Company and all other corporations collectively which are
then Participating Companies.

                           (q)      "PURCHASE DATE" means, for any Purchase
Period, the last day of such period.

                           (r)      "PURCHASE PERIOD" means a period established
in accordance with Section 6.2.

                           (s)      "PURCHASE PRICE" means the price at which a
share of Stock may be purchased under the Plan, as determined in accordance with
Section 9.

                           (t)      "PURCHASE RIGHT" means an option granted to
a Participant pursuant to the Plan to purchase such shares of Stock as provided
in Section 8, which the Participant may or may not exercise during the Offering
Period in which such option is outstanding. Such option arises from the right of
a Participant to withdraw any accumulated


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payroll deductions of the Participant not previously applied to the purchase of
Stock under the Plan and to terminate participation in the Plan at any time
during an Offering Period.

                           (u)      "REGISTRATION DATE" means the effective date
of the initial registration on Form S-8 of shares of Stock issuable pursuant to
the Plan.

                           (v)      "STOCK" means the common stock of the
Company, as adjusted from time to time in accordance with Section 4.2.

                           (w)      "SUBSCRIPTION AGREEMENT" means a written
agreement in such form as specified by the Company, stating an Employee's
election to participate in the Plan and authorizing payroll deductions under the
Plan from the Employee's Compensation.

                           (x)      "SUBSCRIPTION DATE" means the last business
day prior to the Offering Date of an Offering Period or such earlier date as the
Company shall establish.

                           (y)      "SUBSIDIARY CORPORATION" means any present
or future "subsidiary corporation" of the Company, as defined in Section 424(f)
of the Code.

                  2.2      CONSTRUCTION. Captions and titles contained herein
are for convenience only and shall not affect the meaning or interpretation of
any provision of the Plan. Except when otherwise indicated by the context, the
singular shall include the plural and the plural shall include the singular. Use
of the term "or" is not intended to be exclusive, unless the context clearly
requires otherwise.

         3.       ADMINISTRATION.

                  3.1      ADMINISTRATION BY THE BOARD. The Plan shall be
administered by the Board. All questions of interpretation of the Plan, of any
form of agreement or other document employed by the Company in the
administration of the Plan, or of any Purchase Right shall be determined by the
Board, and such determinations shall be final, binding and conclusive upon all
persons having an interest in the Plan or the Purchase Right, unless fraudulent
or made in bad faith. Subject to the provisions of the Plan, the Board shall
determine all of the relevant terms and conditions of Purchase Rights; provided,
however, that all Participants granted Purchase Rights pursuant to an Offering
shall have the same rights and privileges within the meaning of Section
423(b)(5) of the Code. Any and all actions, decisions and determinations taken
or made by the Board in the exercise of its discretion pursuant to the Plan or
any agreement thereunder (other than determining questions of interpretation
pursuant to the second sentence of this Section 3.1) shall be final, binding and
conclusive upon all persons having an interest therein. All expenses incurred in
connection with the administration of the Plan shall be paid by the Company.

                  3.2      AUTHORITY OF OFFICERS. Any officer of the Company
shall have the authority to act on behalf of the Company with respect to any
matter, right, obligation, determination or election that is the responsibility
of or that is allocated to the Company herein, provided that the officer has
apparent authority with respect to such matter, right, obligation, determination
or election.


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                  3.3      POLICIES AND PROCEDURES ESTABLISHED BY THE COMPANY.
The Company may, from time to time, consistent with the Plan and the
requirements of Section 423 of the Code, establish, change or terminate such
rules, guidelines, policies, procedures, limitations, or adjustments as deemed
advisable by the Company, in its discretion, for the proper administration of
the Plan, including, without limitation, (a) a minimum payroll deduction amount
required for participation in an Offering, (b) a limitation on the frequency or
number of changes permitted in the rate of payroll deduction during an Offering,
(c) an exchange ratio applicable to amounts withheld in a currency other than
United States dollars, (d) a payroll deduction greater than or less than the
amount designated by a Participant in order to adjust for the Company's delay or
mistake in processing a Subscription Agreement or in otherwise effecting a
Participant's election under the Plan or as advisable to comply with the
requirements of Section 423 of the Code, and (e) determination of the date and
manner by which the Fair Market Value of a share of Stock is determined for
purposes of administration of the Plan. All such actions by the Company shall be
taken consistent with the requirement under Section 423(b)(5) of the Code that
all Participants granted Purchase Rights pursuant to an Offering shall have the
same rights and privileges within the meaning of such section.

                  3.4      INDEMNIFICATION. In addition to such other rights of
indemnification as they may have as members of the Board or officers or
employees of the Participating Company Group, members of the Board and any
officers or employees of the Participating Company Group to whom authority to
act for the Board or the Company is delegated shall be indemnified by the
Company against all reasonable expenses, including attorneys' fees, actually and
necessarily incurred in connection with the defense of any action, suit or
proceeding, or in connection with any appeal therein, to which they or any of
them may be a party by reason of any action taken or failure to act under or in
connection with the Plan, or any right granted hereunder, and against all
amounts paid by them in settlement thereof (provided such settlement is approved
by independent legal counsel selected by the Company) or paid by them in
satisfaction of a judgment in any such action, suit or proceeding, except in
relation to matters as to which it shall be adjudged in such action, suit or
proceeding that such person is liable for gross negligence, bad faith or
intentional misconduct in duties; provided, however, that within sixty (60) days
after the institution of such action, suit or proceeding, such person shall
offer to the Company, in writing, the opportunity at its own expense to handle
and defend the same.

         4.       SHARES SUBJECT TO PLAN.

                  4.1      MAXIMUM NUMBER OF SHARES ISSUABLE. Subject to
adjustment as provided in Section 4.2, the maximum aggregate number of shares of
Stock that may be issued under the Plan shall be three hundred thousand
(300,000), cumulatively increased on January 1, 2003 and each January 1
thereafter until and including January 1, 2012 (the "ANNUAL INCREASE") by the
lesser of (a) 1% of the number of shares of Stock issued and outstanding on the
immediately preceding December 31, (b) three hundred thousand (300,000) shares,
or (c) such lesser number of shares determined by the Board, and shall consist
of authorized but unissued or reacquired shares of Stock, or any combination
thereof. If an outstanding Purchase Right for any reason expires or is
terminated or canceled, the shares of Stock allocable to the unexercised portion
of that Purchase Right shall again be available for issuance under the Plan.


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                  4.2      ADJUSTMENTS FOR CHANGES IN CAPITAL STRUCTURE. In the
event of any stock dividend, stock split, reverse stock split, recapitalization,
combination, reclassification or similar change in the capital structure of the
Company, or in the event of any merger (including a merger effected for the
purpose of changing the Company's domicile), sale of assets or other
reorganization in which the Company is a party, appropriate adjustments shall be
made in the number and class of shares subject to the Plan, the Annual Increase,
the limit on the shares which may be purchased by any Participant during an
Offering (as described in Section 8.1) and each Purchase Right, and in the
Purchase Price. If a majority of the shares of the same class as the shares
subject to outstanding Purchase Rights are exchanged for, converted into, or
otherwise become (whether or not pursuant to an Ownership Change Event) shares
of another corporation (the "NEW SHARES"), the Board may unilaterally amend the
outstanding Purchase Rights to provide that such Purchase Rights are exercisable
for New Shares. In the event of any such amendment, the number of shares subject
to, and the Purchase Price of, the outstanding Purchase Rights shall be adjusted
in a fair and equitable manner, as determined by the Board, in its discretion.
Notwithstanding the foregoing, any fractional share resulting from an adjustment
pursuant to this Section 4.2 shall be rounded down to the nearest whole number,
and in no event may the Purchase Price be decreased to an amount less than the
par value, if any, of the stock subject to the Purchase Right. The adjustments
determined by the Board pursuant to this Section 4.2 shall be final, binding and
conclusive.

         5.       ELIGIBILITY.

                  5.1      EMPLOYEES ELIGIBLE TO PARTICIPATE. Each Employee of a
Participating Company is eligible to participate in the Plan and shall be deemed
an Eligible Employee, except the following:

                           (a)      Any Employee who is customarily employed by
the Participating Company Group for less than twenty (20) hours per week; or

                           (b)      Any Employee who is customarily employed by
the Participating Company Group for not more than five (5) months in any
calendar year.

                  5.2      EXCLUSION OF CERTAIN STOCKHOLDERS. Notwithstanding
any provision of the Plan to the contrary, no Employee shall be treated as an
Eligible Employee and granted a Purchase Right under the Plan if, immediately
after such grant, the Employee would own or hold options to purchase stock of
the Company or of any Parent Corporation or Subsidiary Corporation possessing
five percent (5%) or more of the total combined voting power or value of all
classes of stock of such corporation, as determined in accordance with Section
423(b)(3) of the Code. For purposes of this Section 5.2, the attribution rules
of Section 424(d) of the Code shall apply in determining the stock ownership of
such Employee.

                  5.3      DETERMINATION BY COMPANY. The Company shall determine
in good faith and in the exercise of its discretion whether an individual has
become or has ceased to be an Employee or an Eligible Employee and the effective
date of such individual's attainment or termination of such status, as the case
may be. For purposes of an individual's participation in or other rights, if
any, under the Plan as of the time of the Company's determination, all such
determinations by the Company shall be final, binding and conclusive,
notwithstanding that the


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Company or any court of law or governmental agency subsequently makes a contrary
determination.

         6.       OFFERINGS.

                  6.1      OFFERING PERIODS. The Plan shall be implemented on
and after the Effective Date by sequential and overlapping Offerings of
approximately twenty four (24) months duration or such other duration as the
Board shall determine (an "OFFERING PERIOD"); provided, however, that the first
Offering Period (the "INITIAL OFFERING PERIOD") shall commence on the Effective
Date and end on April 30, 2004. Subsequent Offering Periods shall commence on or
about May and November of each year and end on or about the last days of the
second April and October, respectively, occurring thereafter. Notwithstanding
the foregoing, the Board may establish a different duration for one or more
Offering Periods or different commencing or ending dates for such Offering
Periods; provided, however, that no Offering Period may have a duration
exceeding twenty-seven (27) months. If the first or last day of an Offering
Period is not a day on which the national securities exchanges or Nasdaq Stock
Market are open for trading, the Company shall specify the trading day that will
be deemed the first or last day, as the case may be, of the Offering Period.

                  6.2      PURCHASE PERIODS. Each Offering Period shall consist
of four (4) consecutive Purchase Periods of approximately six (6) months
duration, or such other number or duration as the Board shall determine
(individually, a "PURCHASE Period"). A Purchase Period commencing on or about
May 1 shall end on or about the next October 31. A Purchase Period commencing on
or about November 1 shall end on or about the next April 30. Notwithstanding the
foregoing, the Board may establish a different duration for one or more Purchase
Periods or different commencing or ending dates for such Purchase Periods. If
the first or last day of a Purchase Period is not a day on which the national
securities exchanges or Nasdaq Stock Market are open for trading, the Company
shall specify the trading day that will be deemed the first or last day, as the
case may be, of the Purchase Period.

         7.       PARTICIPATION IN THE PLAN.

                  7.1      INITIAL PARTICIPATION.

                           (a)      GENERALLY. Except as provided in Section
7.1(b), an Eligible Employee may become a Participant in an Offering Period by
delivering a properly completed Subscription Agreement to the office designated
by the Company not later than the close of business for such office on the
Subscription Date established by the Company for that Offering Period. An
Eligible Employee who does not deliver a properly completed Subscription
Agreement to the Company's designated office on or before the Subscription Date
for an Offering Period shall not participate in the Plan for that Offering
Period or for any subsequent Offering Period unless the Eligible Employee
subsequently delivers a properly completed Subscription Agreement to the
appropriate office of the Company on or before the Subscription Date for such
subsequent Offering Period. An Employee who becomes an Eligible Employee after
the Offering Date of an Offering Period shall not be eligible to participate in
that Offering Period but may participate in any subsequent Offering Period
provided the Employee is still an Eligible Employee as of the Offering Date of
such subsequent Offering Period.


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                           (b)      AUTOMATIC PARTICIPATION IN INITIAL OFFERING
PERIOD. Notwithstanding Section 7.1(a), each Employee who is an Eligible
Employee as of the Effective Date shall automatically become a Participant in
the Initial Offering Period and shall be granted automatically a Purchase Right
consisting of an option to purchase the lesser of (a) a number of whole shares
of Stock determined in accordance with Section 8 or (b) a number of whole shares
of Stock determined by dividing fifteen percent (15%) of such Participant's
Compensation paid during the Initial Offering Period by the Purchase Price
applicable to the Initial Offering Period. The Company shall not require or
permit any Participant to deliver a Subscription Agreement for participation in
the Initial Offering Period; provided, however, that following the Registration
Date a Participant may deliver a Subscription Agreement to the office designated
by the Company if the Participant wishes to change the terms of the
Participant's participation in the Initial Offering Period. Such changes may
include, for example, an election to commence payroll deductions in accordance
with Section 10.

                  7.2      CONTINUED PARTICIPATION.

                           (a)      GENERALLY. Except as provided in Section
7.2(b), a Participant shall automatically participate in the next Offering
Period commencing immediately after the final Purchase Date of each Offering
Period in which the Participant participates provided that the Participant
remains an Eligible Employee on the Offering Date of the new Offering Period and
has not either (a) withdrawn from the Plan pursuant to Section 12.1 or (b)
terminated employment as provided in Section 13. A Participant who may
automatically participate in a subsequent Offering Period, as provided in this
Section, is not required to deliver any additional Subscription Agreement for
the subsequent Offering Period in order to continue participation in the Plan.
However, a Participant may deliver a new Subscription Agreement for a subsequent
Offering Period in accordance with the procedures set forth in Section 7.1(a) if
the Participant desires to change any of the elections contained in the
Participant's then effective Subscription Agreement.

                           (b)      PARTICIPATION IN SUBSEQUENT OFFERING PERIOD.
Notwithstanding Section 7.2(a), an Eligible Employee who was automatically
enrolled in the Initial Offering Period and who wishes to participate in an
Offering Period which begins after the Initial Offering Period shall deliver a
Subscription Agreement in accordance with Section 7.1(a) no earlier than the
Registration Date and no later than the Subscription Date for such Offering
Period, unless such Employee was a Participant in the Initial Offering Period
who delivered a Subscription Agreement with respect to the Initial Offering
Period as provided in Section 7.1(b).

         8.       RIGHT TO PURCHASE SHARES.

                  8.1      GRANT OF PURCHASE RIGHT. Except as provided in
Section 7.1 with respect to the Initial Offering Period or as set forth below
(or otherwise specified by the Board prior to the Offering Date), on the
Offering Date of each Offering Period, each Participant in such Offering Period
shall be granted automatically, on the Offering Date, a Purchase Right
consisting of an option to purchase the lesser of (a) that number of whole
shares of Stock determined by dividing Fifty Thousand Dollars ($50,000) by the
Fair Market Value of a share of Stock on such Offering Date or (b) five
thousand (5,000) shares of Stock. No Purchase Right shall be


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granted on an Offering Date to any person who is not, on such Offering Date, an
Eligible Employee.

                  8.2      PRO RATA ADJUSTMENT OF PURCHASE RIGHT.
Notwithstanding the provisions of Section 8.1, if the Board establishes an
Offering Period of any duration other than twenty four months, then (a) the
dollar amount in Section 8.1 shall be determined by multiplying $2,083.33 by the
number of months (rounded to the nearest whole month) in the Offering Period and
rounding to the nearest whole dollar, and (b) the share amount in Section 8.1
shall be determined by multiplying 208.33 shares by the number of months
(rounded to the nearest whole month) in the Offering Period and rounding to the
nearest whole share.

                  8.3      CALENDAR YEAR PURCHASE LIMITATION. Notwithstanding
any provision of the Plan to the contrary, no Participant shall be granted a
Purchase Right which permits his or her right to purchase shares of Stock under
the Plan to accrue at a rate which, when aggregated with such Participant's
rights to purchase shares under all other employee stock purchase plans of a
Participating Company intended to meet the requirements of Section 423 of the
Code, exceeds Twenty-Five Thousand Dollars ($25,000) in Fair Market Value (or
such other limit, if any, as may be imposed by the Code) for each calendar year
in which such Purchase Right is outstanding at any time. For purposes of the
preceding sentence, the Fair Market Value of shares purchased during a given
Offering Period shall be determined as of the Offering Date for such Offering
Period. The limitation described in this Section shall be applied in conformance
with applicable regulations under Section 423(b)(8) of the Code.

         9.       PURCHASE PRICE.

                  The Purchase Price at which each share of Stock may be
acquired in an Offering Period upon the exercise of all or any portion of a
Purchase Right shall be established by the Board; provided, however, that the
Purchase Price on each Purchase Date shall not be less than eighty-five percent
(85%) of the lesser of (a) the Fair Market Value of a share of Stock on the
Offering Date of the Offering Period or (b) the Fair Market Value of a share of
Stock on the Purchase Date. Unless otherwise provided by the Board prior to the
commencement of an Offering Period, the Purchase Price on each Purchase Date
during that Offering Period shall be eighty-five percent (85%) of the lesser of
(a) the Fair Market Value of a share of Stock on the Offering Date of the
Offering Period, or (b) the Fair Market Value of a share of Stock on the
Purchase Date.

         10.      ACCUMULATION OF PURCHASE PRICE THROUGH PAYROLL DEDUCTION.

                  Except as provided in Section 11.1(b) with respect to the
Initial Offering Period, shares of Stock acquired pursuant to the exercise of
all or any portion of a Purchase Right may be paid for only by means of payroll
deductions from the Participant's Compensation accumulated during the Offering
Period for which such Purchase Right was granted, subject to the following:

                  10.1     AMOUNT OF PAYROLL DEDUCTIONS. Except as otherwise
provided herein, the amount to be deducted under the Plan from a Participant's
Compensation on each payday during an Offering Period shall be determined by the
Participant's Subscription Agreement. The


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Subscription Agreement shall set forth the percentage of the Participant's
Compensation to be deducted on each payday during an Offering Period in whole
percentages of not less than one percent (1%) (except as a result of an election
pursuant to Section 10.3 to stop payroll deductions effective following the
first payday during an Offering) or more than fifteen percent (15%). The Board
may change the foregoing limits on payroll deductions effective as of any
Offering Date.

                  10.2     COMMENCEMENT OF PAYROLL DEDUCTIONS. Payroll
deductions shall commence on the first payday following the Offering Date and
shall continue to the end of the Offering Period unless sooner altered or
terminated as provided herein; provided, however, that with respect to the
Initial Offering Period, payroll deductions shall commence as soon as
practicable following the Company's receipt of the Participant's Subscription
Agreement (delivered no earlier than the Registration Date), if any.

                  10.3     ELECTION TO CHANGE OR STOP PAYROLL DEDUCTIONS. During
an Offering Period, a Participant may elect to stop deductions from his or her
Compensation by delivering to the Company's designated office an amended
Subscription Agreement authorizing such change on or before the Change Notice
Date, as defined below. A Participant who elects, effective following the first
payday of an Offering Period, to decrease the rate of his or her payroll
deductions to zero percent (0%) shall nevertheless remain a Participant in the
current Offering Period unless such Participant withdraws from the Plan as
provided in Section 12.1. The "CHANGE NOTICE DATE" shall be the day immediately
prior to the beginning of the first pay period for which such election is to be
effective, unless a different date is established by the Company and announced
to the Participants. Except as otherwise described above, a Participant may not
elect to increase or decrease deductions from his or her Compensation during an
Offering.

                  10.4     ADMINISTRATIVE SUSPENSION OF PAYROLL DEDUCTIONS. The
Company may, in its sole discretion, suspend a Participant's payroll deductions
under the Plan as the Company deems advisable to avoid accumulating payroll
deductions in excess of the amount that could reasonably be anticipated to
purchase the maximum number of shares of Stock permitted (a) under the
Participant's Purchase Right or (b) during a calendar year under the limit set
forth in Section 8.3. Payroll deductions shall be resumed at the rate specified
in the Participant's then effective Subscription Agreement at the beginning,
respectively, of (a) the next Offering Period the first Purchase Date of which
falls in the following calendar year, provided that the individual is a
Participant in such Offering Period or (b) the next Purchase Period the Purchase
Date of which falls in the following calendar year, unless the Participant has
either withdrawn from the Plan as provided in Section 12.1 or has ceased to be
an Eligible Employee.

                  10.5     PARTICIPANT ACCOUNTS. Individual bookkeeping accounts
shall be maintained for each Participant. All payroll deductions from a
Participant's Compensation (and other amounts received from the Participant in
the Initial Offering Period) shall be credited to such Participant's Plan
account and shall be deposited with the general funds of the Company. All such
amounts received or held by the Company may be used by the Company for any
corporate purpose.


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                  10.6     NO INTEREST PAID. Interest shall not be paid on sums
deducted from a Participant's Compensation pursuant to the Plan or otherwise
credited to the Participant's Plan account.

         11.      PURCHASE OF SHARES.

                  11.1     EXERCISE OF PURCHASE RIGHT.

                           (a)      GENERALLY. Except as provided in Section
11.1(b), on each Purchase Date of an Offering Period, each Participant who has
not withdrawn from the Plan and whose participation in the Offering has not
otherwise terminated before such Purchase Date shall automatically acquire
pursuant to the exercise of the Participant's Purchase Right the number of whole
shares of Stock determined by dividing (a) the total amount of the Participant's
payroll deductions accumulated in the Participant's Plan account during the
Offering Period and not previously applied toward the purchase of Stock by (b)
the Purchase Price. However, in no event shall the number of shares purchased by
the Participant during an Offering Period exceed the number of shares subject to
the Participant's Purchase Right. No shares of Stock shall be purchased on a
Purchase Date on behalf of a Participant whose participation in the Offering or
the Plan has terminated before such Purchase Date.

                           (b)      PURCHASE IN INITIAL OFFERING PERIOD.
Notwithstanding Section 11.1(a), on each Purchase Date of the Initial Offering
Period, each Participant who has not withdrawn from the Plan and whose
participation in such Offering has not otherwise terminated before such Purchase
Date shall automatically acquire pursuant to the exercise of the Participant's
Purchase Right (i) a number of whole shares of Stock determined in accordance
with Section 11.1(a) to the extent of the total amount of the Participant's
payroll deductions accumulated in the Participant's Plan account during the
Initial Offering Period, if any, and not previously applied toward the purchase
of Stock and (ii) such additional shares of Stock (not exceeding in the
aggregate the Participant's Purchase Right) as determined in accordance with an
Initial Offering Period Cash Exercise Notice delivered to the office designated
by the Company no earlier than the Registration Date and not later than the
close of business for such office on the last business day immediately preceding
the Purchase Date or such earlier date as the Company shall establish,
accompanied by payment in cash or by check of the Purchase Price for such
additional shares. However, in no event shall the number of shares purchased by
a Participant during the Initial Offering Period exceed the number of shares
subject to the Participant's Purchase Right. In addition, if a Participant
delivers a Subscription Agreement to the Company after the Registration Date,
the Participant may not elect to exercise a Purchase Right pursuant to an
Initial Offering Period Cash Exercise Notice in an amount which exceeds fifteen
percent (15%) of the Compensation paid such Participant prior to the
effectiveness of such initial Subscription Agreement. The Company shall refund
to the Participant in accordance with Section 11.4 any excess Purchase Price
payment received from the Participant.

                  11.2     PRO RATA ALLOCATION OF SHARES. If the number of
shares of Stock which might be purchased by all Participants in the Plan on a
Purchase Date exceeds the number of shares of Stock available in the Plan as
provided in Section 4.1, the Company shall make a pro rata allocation of the
remaining shares in as uniform a manner as practicable and as the Company


                                       11
<Page>


determines to be equitable. Any fractional share resulting from such pro rata
allocation to any Participant shall be disregarded.

                  11.3     DELIVERY OF CERTIFICATES. As soon as practicable
after each Purchase Date, the Company shall arrange the delivery to each
Participant of a certificate representing the shares acquired by the Participant
on such Purchase Date; provided that the Company may deliver such shares to a
broker designated by the Company that will hold such shares for the benefit of
the Participant. Shares to be delivered to a Participant under the Plan shall be
registered in the name of the Participant, or, if requested by the Participant,
in the name of the Participant and his or her spouse, or, if applicable, in the
names of the heirs of the Participant.

                  11.4     RETURN OF CASH BALANCE. Any cash balance remaining in
a Participant's Plan account following any Purchase Date shall be refunded to
the Participant as soon as practicable after such Purchase Date. However, if the
cash balance to be returned to a Participant pursuant to the preceding sentence
is less than the amount that would have been necessary to purchase an additional
whole share of Stock on such Purchase Date, the Company may retain the cash
balance in the Participant's Plan account to be applied toward the purchase of
shares of Stock in the subsequent Purchase Period or Offering Period, as the
case may be.

                  11.5     TAX WITHHOLDING. At the time a Participant's Purchase
Right is exercised, in whole or in part, or at the time a Participant disposes
of some or all of the shares of Stock he or she acquires under the Plan, the
Participant shall make adequate provision for the federal, state, local and
foreign tax withholding obligations, if any, of the Participating Company Group
which arise upon exercise of the Purchase Right or upon such disposition of
shares, respectively. The Participating Company Group may, but shall not be
obligated to, withhold from the Participant's compensation the amount necessary
to meet such withholding obligations.

                  11.6     EXPIRATION OF PURCHASE RIGHT. Any portion of a
Participant's Purchase Right remaining unexercised after the end of the Offering
Period to which the Purchase Right relates shall expire immediately upon the end
of the Offering Period.

                  11.7     PROVISION OF REPORTS AND STOCKHOLDER INFORMATION TO
PARTICIPANTS. Each Participant who has exercised all or part of his or her
Purchase Right shall receive, as soon as practicable after the Purchase Date, a
report of such Participant's Plan account setting forth the total amount
credited to his or her Plan account prior to such exercise, the number of shares
of Stock purchased, the Purchase Price for such shares, the date of purchase and
the cash balance, if any, remaining immediately after such purchase that is to
be refunded or retained in the Participant's Plan account pursuant to Section
11.4. The report required by this Section may be delivered in such form and by
such means, including by electronic transmission, as the Company may determine.
In addition, each Participant shall be provided information concerning the
Company equivalent to that information provided generally to the Company's
common stockholders.

         12.      WITHDRAWAL FROM PLAN OR OFFERING.

                  12.1     VOLUNTARY WITHDRAWAL FROM THE PLAN. A Participant may
withdraw from the Plan by signing and delivering to the Company's designated
office a written notice of


                                       12
<Page>


withdrawal on a form provided by the Company for this purpose. Such withdrawal
may be elected at any time prior to the end of an Offering Period; provided,
however, that if a Participant withdraws from the Plan after a Purchase Date,
the withdrawal shall not affect shares of Stock acquired by the Participant on
such Purchase Date. A Participant who voluntarily withdraws from the Plan is
prohibited from resuming participation in the Plan in the same Offering from
which he or she withdrew, but may participate in any subsequent Offering by
again satisfying the requirements of Sections 5 and 7.1. The Company may impose,
from time to time, a requirement that the notice of withdrawal from the Plan be
on file with the Company's designated office for a reasonable period prior to
the effectiveness of the Participant's withdrawal.

                  12.2     AUTOMATIC WITHDRAWAL FROM AN OFFERING. If the Fair
Market Value of a share of Stock on a Purchase Date other than the final
Purchase Date of an Offering is less than the Fair Market Value of a share of
Stock on the Offering Date of the Offering, then every Participant (except for a
Participant in the Initial Offering Period who did not deliver a Subscription
Agreement prior to such Purchase Date) automatically shall be (a) withdrawn from
such Offering after the acquisition of shares of Stock on the Purchase Date and
(b) enrolled in the new Offering commencing immediately following such Purchase
Date. A Participant may elect not to be automatically withdrawn from an from an
Offering pursuant to this Section 12.2 by delivering to the Company's designated
office not later than the close of business on the Purchase Date a written
notice indicating such election.

                  12.3     RETURN OF PAYROLL DEDUCTIONS. Upon a Participant's
voluntary withdrawal from the Plan pursuant to Section 12.1 or automatic
withdrawal from an Offering pursuant to Section 12.2, the Participant's
accumulated Plan account balance which has not been applied toward the purchase
of shares of Stock (except, in the case of an automatic withdrawal pursuant to
Section 12.2, for an amount necessary to purchase an additional whole share of
Stock as provided in Section 11.4) shall be refunded to the Participant as soon
as practicable after the withdrawal, without the payment of any interest, and
the Participant's interest in the Plan or the Offering, as applicable, shall
terminate. Such amounts to be refunded in accordance with this Section may not
be applied to any other Offering under the Plan.

         13.      TERMINATION OF EMPLOYMENT OR ELIGIBILITY.

                  Upon a Participant's ceasing, prior to a Purchase Date, to be
an Employee of the Participating Company Group for any reason, including
retirement, disability or death, or upon the failure of a Participant to remain
an Eligible Employee, the Participant's participation in the Plan shall
terminate immediately. In such event, the Participant's Plan account balance
which has not been applied toward the purchase of shares shall, as soon as
practicable, be returned to the Participant or, in the case of the Participant's
death, to the Participant's beneficiary designated in accordance with Section
20, if any, or legal representative, and all of the Participant's rights under
the Plan shall terminate. Interest shall not be paid on sums returned pursuant
to this Section 13. A Participant whose participation has been so terminated may
again become eligible to participate in the Plan by satisfying the requirements
of Sections 5 and 7.1.


                                       13
<Page>


         14.      CHANGE IN CONTROL.

                  14.1     DEFINITIONS.

                           (a)      An "OWNERSHIP CHANGE EVENT" shall be deemed
to have occurred if any of the following occurs with respect to the Company: (i)
the direct or indirect sale or exchange in a single or series of related
transactions by the stockholders of the Company of more than fifty percent (50%)
of the voting stock of the Company; (ii) a merger or consolidation in which the
Company is a party; (iii) the sale, exchange, or transfer of all or
substantially all of the assets of the Company; or (iv) a liquidation or
dissolution of the Company.

                           (b)      A "CHANGE IN CONTROL" shall mean an
Ownership Change Event or a series of related Ownership Change Events
(collectively, the "TRANSACTION") wherein the stockholders of the Company
immediately before the Transaction do not retain immediately after the
Transaction, in substantially the same proportions as their ownership of shares
of the Company's voting stock immediately before the Transaction, direct or
indirect beneficial ownership of more than fifty percent (50%) of the total
combined voting power of the outstanding voting securities of the Company or, in
the case of a Transaction described in Section 14.1(a)(iii), the corporation or
other business entity to which the assets of the Company were transferred (the
"TRANSFEREE"), as the case may be. For purposes of the preceding sentence,
indirect beneficial ownership shall include, without limitation, an interest
resulting from ownership of the voting securities of one or more corporations or
other business entities which own the Company or the Transferee, as the case may
be, either directly or through one or more subsidiary corporations or other
business entities. The Board shall have the right to determine whether multiple
sales or exchanges of the voting securities of the Company or multiple Ownership
Change Events are related, and its determination shall be final, binding and
conclusive.

                  14.2     EFFECT OF CHANGE IN CONTROL ON PURCHASE RIGHTS. In
the event of a Change in Control, the surviving, continuing, successor, or
purchasing corporation or other business entity or parent thereof, as the case
may be (the "ACQUIRING CORPORATION"), may, without the consent of any
Participant, assume the Company's rights and obligations under the Plan. If the
Acquiring Corporation elects not to assume the Company's rights and obligations
under the Plan, the Purchase Date of the then current Purchase Period shall be
accelerated to a date before the date of the Change in Control specified by the
Board, but the number of shares of Stock subject to outstanding Purchase Rights
shall not be adjusted. All Purchase Rights which are neither assumed by the
Acquiring Corporation in connection with the Change in Control nor exercised as
of the date of the Change in Control shall terminate and cease to be outstanding
effective as of the date of the Change in Control.

         15.      NONTRANSFERABILITY OF PURCHASE RIGHTS.

                  Neither payroll deductions or other amounts credited to a
Participant's Plan account nor a Participant's Purchase Right may be assigned,
transferred, pledged or otherwise disposed of in any manner other than as
provided by the Plan or by will or the laws of descent and distribution. (A
beneficiary designation pursuant to Section 20 shall not be treated as a
disposition for this purpose.) Any such attempted assignment, transfer, pledge
or other


                                       14
<Page>


disposition shall be without effect, except that the Company may treat such act
as an election to withdraw from the Plan as provided in Section 12.1. A Purchase
Right shall be exercisable during the lifetime of the Participant only by the
Participant.

         16.      COMPLIANCE WITH SECURITIES LAW.

                  The issuance of shares under the Plan shall be subject to
compliance with all applicable requirements of federal, state and foreign law
with respect to such securities. A Purchase Right may not be exercised if the
issuance of shares upon such exercise would constitute a violation of any
applicable federal, state or foreign securities laws or other law or regulations
or the requirements of any securities exchange or market system upon which the
Stock may then be listed. In addition, no Purchase Right may be exercised unless
(a) a registration statement under the Securities Act of 1933, as amended, shall
at the time of exercise of the Purchase Right be in effect with respect to the
shares issuable upon exercise of the Purchase Right, or (b) in the opinion of
legal counsel to the Company, the shares issuable upon exercise of the Purchase
Right may be issued in accordance with the terms of an applicable exemption from
the registration requirements of said Act. The inability of the Company to
obtain from any regulatory body having jurisdiction the authority, if any,
deemed by the Company's legal counsel to be necessary to the lawful issuance and
sale of any shares under the Plan shall relieve the Company of any liability in
respect of the failure to issue or sell such shares as to which such requisite
authority shall not have been obtained. As a condition to the exercise of a
Purchase Right, the Company may require the Participant to satisfy any
qualifications that may be necessary or appropriate, to evidence compliance with
any applicable law or regulation, and to make any representation or warranty
with respect thereto as may be requested by the Company.

         17.      RIGHTS AS A STOCKHOLDER AND EMPLOYEE.

                  A Participant shall have no rights as a stockholder by virtue
of the Participant's participation in the Plan until the date of the issuance of
a certificate for the shares purchased pursuant to the exercise of the
Participant's Purchase Right (as evidenced by the appropriate entry on the books
of the Company or of a duly authorized transfer agent of the Company). No
adjustment shall be made for dividends, distributions or other rights for which
the record date is prior to the date such certificate is issued, except as
provided in Section 4.2. Nothing herein shall confer upon a Participant any
right to continue in the employ of the Participating Company Group or interfere
in any way with any right of the Participating Company Group to terminate the
Participant's employment at any time.

         18.      LEGENDS.

                  The Company may at any time place legends or other identifying
symbols referencing any applicable federal, state or foreign securities law
restrictions or any provision convenient in the administration of the Plan on
some or all of the certificates representing shares of Stock issued under the
Plan. The Participant shall, at the request of the Company, promptly present to
the Company any and all certificates representing shares acquired pursuant to a
Purchase Right in the possession of the Participant in order to carry out the
provisions of this


                                       15
<Page>


Section. Unless otherwise specified by the Company, legends placed on such
certificates may include but shall not be limited to the following:

"THE SHARES EVIDENCED BY THIS CERTIFICATE WERE ISSUED BY THE CORPORATION TO THE
REGISTERED HOLDER UPON THE PURCHASE OF SHARES UNDER AN EMPLOYEE STOCK PURCHASE
PLAN AS DEFINED IN SECTION 423 OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED.
THE TRANSFER AGENT FOR THE SHARES EVIDENCED HEREBY SHALL NOTIFY THE CORPORATION
IMMEDIATELY OF ANY TRANSFER OF THE SHARES BY THE REGISTERED HOLDER HEREOF. THE
REGISTERED HOLDER SHALL HOLD ALL SHARES PURCHASED UNDER THE PLAN IN THE
REGISTERED HOLDER'S NAME (AND NOT IN THE NAME OF ANY NOMINEE)."

         19.      NOTIFICATION OF DISPOSITION OF SHARES.

                  The Company may require the Participant to give the Company
prompt notice of any disposition of shares acquired by exercise of a Purchase
Right. The Company may require that until such time as a Participant disposes of
shares acquired upon exercise of a Purchase Right, the Participant shall hold
all such shares in the Participant's name (or, if elected by the Participant, in
the name of the Participant and his or her spouse but not in the name of any
nominee) until the later of two years after the date of grant of such Purchase
Right or one year after the date of exercise of such Purchase Right. The Company
may direct that the certificates evidencing shares acquired by exercise of a
Purchase Right refer to such requirement to give prompt notice of disposition.

         20.      DESIGNATION OF BENEFICIARY.

                  20.1     DESIGNATION PROCEDURE. A Participant may file a
written designation of a beneficiary who is to receive (a) shares and cash, if
any, from the Participant's Plan account if the Participant dies subsequent to a
Purchase Date but prior to delivery to the Participant of such shares and cash
or (b) cash, if any, from the Participant's Plan account if the Participant dies
prior to the exercise of the Participant's Purchase Right. If a married
Participant designates a beneficiary other than the Participant's spouse, the
effectiveness of such designation shall be subject to the consent of the
Participant's spouse. A Participant may change his or her beneficiary
designation at any time by written notice to the Company.

                  20.2     ABSENCE OF BENEFICIARY DESIGNATION. If a Participant
dies without an effective designation pursuant to Section 20.1 of a beneficiary
who is living at the time of the Participant's death, the Company shall deliver
any shares or cash credited to the Participant's Plan account to the
Participant's legal representative.

         21.      NOTICES.

                  All notices or other communications by a Participant to the
Company under or in connection with the Plan shall be deemed to have been duly
given when received in the form specified by the Company at the location, or by
the person, designated by the Company for the receipt thereof.


                                       16
<Page>


         22.      AMENDMENT OR TERMINATION OF THE PLAN.

                  The Board may at any time amend or terminate the Plan, except
that (a) no such amendment or termination shall affect Purchase Rights
previously granted under the Plan unless expressly provided by the Board and (b)
no such amendment or termination may adversely affect a Purchase Right
previously granted under the Plan without the consent of the Participant, except
to the extent permitted by the Plan or as may be necessary to qualify the Plan
as an employee stock purchase plan pursuant to Section 423 of the Code or to
comply with any applicable law, regulation or rule. In addition, an amendment to
the Plan must be approved by the stockholders of the Company within twelve (12)
months of the adoption of such amendment if such amendment would authorize the
sale of more shares than are then authorized for issuance under the Plan or
would change the definition of the corporations that may be designated by the
Board as Participating Companies.


                                       17
<Page>


                                  PLAN HISTORY


April 17, 2002              Board of Directors of MitoKor, Inc., a California
                            corporation ("MitoKor California") adopts the Plan,
                            with an initial reserve of 300,000 shares. The Board
                            also established that the share reserve will be
                            increased cumulatively on each January 1 from
                            January 1, 2003 through January 1, 2012 by the
                            lesser of (i) 1% of the shares of common stock
                            issued and outstanding on the immediately preceding
                            December 31, (ii) 300,000 shares, or (iii) such
                            lesser number of shares determined by the Board.

______________, 2002        Shareholders of MitoKor California approve Plan.

______________, 2002        Effective date of Delaware reincorporation of
                            MitoKor California.

______________, 2002        Effective Date of the Plan (i.e., date on which
                            Initial Offering Period commenced).


<Page>


                                  MITOKOR, INC.
                        2002 EMPLOYEE STOCK PURCHASE PLAN
                             SUBSCRIPTION AGREEMENT


NAME (Please print):
                    ------------------------------------------------------------
                    (Last)                   (First)                   (Middle)

/ / Original application for the Offering Period beginning (date):______________

/ / Stop payroll deductions effective with the pay period ending (date):________

/ / Change of beneficiary.

I.       SUBSCRIPTION

         I elect to participate in the 2002 Employee Stock Purchase Plan (the
"PLAN") of MitoKor, Inc. (the "COMPANY") and to subscribe to purchase shares of
the Company's Common Stock in accordance with this Subscription Agreement and
the Plan.

         I authorize payroll deductions of __________ percent (in whole
percentages not less than 1%, unless an election to stop deductions is being
made, or more than [15%]) of my "COMPENSATION" on each payday throughout the
"OFFERING PERIOD" in accordance with the Plan. I understand that these payroll
deductions will be accumulated for the purchase of shares of Common Stock at the
applicable purchase price determined in accordance with the Plan. Except as
otherwise provided by the Plan, I will automatically purchase shares on each
"PURCHASE DATE" unless I withdraw from the Plan by giving written notice on a
form provided by the Company or unless my eligibility or employment terminates.

         I understand that I will automatically participate in each subsequent
Offering that commences immediately after the last day of an Offering in which I
am participating until I withdraw from the Plan by giving written notice on a
form provided by the Company or my eligibility or employment terminates.

         Shares I purchase under the Plan should be issued in the name(s) set
forth below. (Shares may be issued in the participant's name alone or together
with the participant's spouse as community property or in joint tenancy.)

         NAME(S) (please print):
                                ------------------------------------------------

         ADDRESS:
                 ---------------------------------------------------------------

         MY SOCIAL SECURITY NUMBER:
                                   ---------------------------------------------

         I agree to make adequate provision for the federal, state, local and
foreign tax withholding obligations, if any, which arise upon my purchase of
shares under the Plan and/or my disposition of shares. The Company may withhold
from my compensation the amount necessary to meet such withholding obligations.

         I agree that, unless otherwise permitted by the Company, until I
dispose of shares I purchase under the Plan, I will hold such shares in the
name(s) entered above (and not in the name of any nominee) until the later of
(i) two years after the first day of the Offering Period in which I purchased
the shares and (ii) one year after the Purchase Date on which I purchased the
shares. This restriction only applies to the name(s) in which shares are held
and does NOT affect my ability to dispose of Plan shares.

         I AGREE THAT I WILL NOTIFY THE CHIEF FINANCIAL OFFICER OF THE COMPANY
IN WRITING WITHIN 30 DAYS AFTER ANY SALE, GIFT, TRANSFER OR OTHER DISPOSITION OF
ANY KIND PRIOR TO THE END OF THE PERIODS REFERRED TO IN THE PRECEDING PARAGRAPH
(A "DISQUALIFYING DISPOSITION") OF ANY SHARES I PURCHASED


                                        1
<Page>


UNDER THE PLAN. IF I DO NOT RESPOND WITHIN 30 DAYS OF THE DATE OF A
DISQUALIFYING DISPOSITION SURVEY DELIVERED TO ME BY CERTIFIED MAIL, THE COMPANY
IS AUTHORIZED TO TREAT MY NONRESPONSE AS MY NOTICE TO THE COMPANY OF A
DISQUALIFYING DISPOSITION AND TO COMPUTE AND REPORT TO THE INTERNAL REVENUE
SERVICE THE ORDINARY INCOME I MUST RECOGNIZE UPON SUCH DISQUALIFYING
DISPOSITION.

II.      BENEFICIARY DESIGNATION

         In the event of my death, I designate the following as my beneficiary
to receive all payments and shares then due me under the Plan:

         BENEFICIARY'S NAME (please print):
                                           ------------------------------------
                                           (First)        (Middle)        (Last)

         RELATIONSHIP:                          SOC. SEC. NO.:
                      ------------------------                ------------------

         ADDRESS:
                 ---------------------------------------------------------------

         If you are married and your beneficiary is someone other than your
spouse, then your spouse must sign and date this form as indicated below. If you
are not married when you designate a beneficiary and you later become married,
or if you later become married to a different person, the beneficiary
designation previously made will be automatically revoked. Payments and shares
then due you upon your death will be delivered to your then spouse unless you
have completed a new beneficiary designation and it is consented to by your then
spouse.

III.     CONSENT OF SPOUSE

         I am the spouse of _____________. I consent to the above designation of
a beneficiary other than me to receive payments and shares due my spouse under
the Plan.



Date:
      ------------------------         -----------------------------------------
                                       Signature of Participant's Spouse

IV.      PARTICIPANT DECLARATION

         Any election I have made on this form revokes all prior elections with
regard to this form.

         I am familiar with the provisions of the Plan and agree to participate
in the Plan subject to all of its provisions. I understand that the Board of
Directors of the Company reserves the right to terminate the Plan or to amend
the Plan and my right to purchase stock under the Plan to the extent provided by
the Plan. I understand that the effectiveness of this Subscription Agreement is
dependent upon my eligibility to participate in the Plan.


Date:
      ------------------------         -----------------------------------------
                                       Signature of Participant


                                       2
<Page>


                                  MITOKOR, INC.
                        2002 EMPLOYEE STOCK PURCHASE PLAN
                              NOTICE OF WITHDRAWAL


NAME (Please print):
                    ------------------------------------------------------------
                    (Last)                  (First)                    (Middle)

         I elect to withdraw from the MitoKor, Inc. 2002 Employee Stock Purchase
Plan (the "PLAN") and the Offering which began on (date) ____________________
and in which I am participating (the "CURRENT OFFERING").


                  I elect to terminate immediately my participation in the
                  Current Offering and the Plan. I request that the Company
                  cease all further payroll deductions under the Plan (provided
                  I have given sufficient notice before the next payday). My
                  payroll deductions not previously used to purchase shares
                  should NOT be used to purchase shares in the Current Offering.
                  Instead, I request that all such amounts be paid to me as soon
                  as practicable. I understand that this election immediately
                  terminates my interest in the Current Offering and in the
                  Plan.

         I understand that I am terminating my interest in the Plan and that no
further payroll deductions will be made (provided I have given sufficient notice
before the next payday), unless I elect to become a participant in another
Offering by filing a new Subscription Agreement with the Company. I understand
that I will receive no interest on the amounts paid to me from my Plan account,
and that I may not apply such amounts to any other Offering under the Plan or
any other employee stock purchase plan of the Company.



Date:                                   Signature:
     -------------------------------              ------------------------------